logd: replace internal CLOCK_MONOTONIC use with sequence numbers

- switch to simpler and faster internal sequence number, drops
  a syscall overhead on 32-bit platforms.
- add ability to break-out of flushTo loop with filter return -1
  allowing in reduction in reader overhead.

Change-Id: Ic5cb2b9afa4d9470153971fc9197b07279e2b79d
diff --git a/logd/LogBuffer.h b/logd/LogBuffer.h
index 86a2a2a..13e6aa8 100644
--- a/logd/LogBuffer.h
+++ b/logd/LogBuffer.h
@@ -51,9 +51,9 @@
     void log(log_id_t log_id, log_time realtime,
              uid_t uid, pid_t pid, pid_t tid,
              const char *msg, unsigned short len);
-    log_time flushTo(SocketClient *writer, const log_time start,
+    uint64_t flushTo(SocketClient *writer, const uint64_t start,
                      bool privileged,
-                     bool (*filter)(const LogBufferElement *element, void *arg) = NULL,
+                     int (*filter)(const LogBufferElement *element, void *arg) = NULL,
                      void *arg = NULL);
 
     void clear(log_id_t id, uid_t uid = AID_ROOT);